How do I apply a texture to only 1 face?
I don't know how it worked in Blender 2.79. But if you want to add texture to a single face you have to go to Edit-Mode and then mark your face. Create a new material and klick on assign. (The Materials Pannel in 2.8 is on the right side of your Viewport.)

Now you should only have the marked face painted, you are able to add textures by pressing: Use Nodes (also in the Material Panel).

I hope my description works for you, if not let me know. 

Greetings Sebbe